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><H1
CLASS="SECT1"
><A
NAME="SSL-TCP"
>17.9. Secure TCP/IP Connections with SSL</A
></H1
><P
>   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> has native support for using
   <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> connections to encrypt client/server communications
   for increased security. This requires that
   <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
> is installed on both client and
   server systems and that support in <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> is
   enabled at build time (see <A
HREF="installation.html"
>Chapter 15</A
>).
  </P
><P
>   With <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> support compiled in, the
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server can be started with
   <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> enabled by setting the parameter
   <A
HREF="runtime-config-connection.html#GUC-SSL"
>ssl</A
> to <TT
CLASS="LITERAL"
>on</TT
> in
   <TT
CLASS="FILENAME"
>postgresql.conf</TT
>.  The server will listen for both normal
   and <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> connections on the same TCP port, and will negotiate
   with any connecting client on whether to use <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
>.  By
   default, this is at the client's option; see <A
HREF="auth-pg-hba-conf.html"
>Section 19.1</A
> about how to set up the server to require
   use of <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> for some or all connections.
  </P
><P
>   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> reads the system-wide
   <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
> configuration file. By default, this
   file is named <TT
CLASS="FILENAME"
>openssl.cnf</TT
> and is located in the
   directory reported by <TT
CLASS="LITERAL"
>openssl version -d</TT
>.
   This default can be overridden by setting environment variable
   <TT
CLASS="ENVAR"
>OPENSSL_CONF</TT
> to the name of the desired configuration file.
  </P
><P
>   <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
> supports a wide range of ciphers
   and authentication algorithms, of varying strength.  While a list of
   ciphers can be specified in the <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
>
   configuration file, you can specify ciphers specifically for use by
   the database server by modifying <A
HREF="runtime-config-connection.html#GUC-SSL-CIPHERS"
>ssl_ciphers</A
> in
   <TT
CLASS="FILENAME"
>postgresql.conf</TT
>.
  </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>    It is possible to have authentication without encryption overhead by
    using <TT
CLASS="LITERAL"
>NULL-SHA</TT
> or <TT
CLASS="LITERAL"
>NULL-MD5</TT
> ciphers.  However,
    a man-in-the-middle could read and pass communications between client
    and server.  Also, encryption overhead is minimal compared to the
    overhead of authentication.  For these reasons NULL ciphers are not
    recommended.
   </P
></BLOCKQUOTE
></DIV
><P
>   To start in <ACRONYM
CLASS="ACRONYM"
>SSL</ACRONYM
> mode, the files <TT
CLASS="FILENAME"
>server.crt</TT
>
   and <TT
CLASS="FILENAME"
>server.key</TT
> must exist in the server's data directory.
   These files should contain the server certificate and private key,
   respectively.
   On Unix systems, the permissions on <TT
CLASS="FILENAME"
>server.key</TT
> must
   disallow any access to world or group; achieve this by the command
   <TT
CLASS="COMMAND"
>chmod 0600 server.key</TT
>.
   If the private key is protected with a passphrase, the
   server will prompt for the passphrase and will not start until it has
   been entered.
  </P
><P
>   In some cases, the server certificate might be signed by an
   <SPAN
CLASS="QUOTE"
>"intermediate"</SPAN
> certificate authority, rather than one that is
   directly trusted by clients.  To use such a certificate, append the
   certificate of the signing authority to the <TT
CLASS="FILENAME"
>server.crt</TT
> file,
   then its parent authority's certificate, and so on up to a <SPAN
CLASS="QUOTE"
>"root"</SPAN
>
   authority that is trusted by the clients.  The root certificate should
   be included in every case where <TT
CLASS="FILENAME"
>server.crt</TT
> contains more than
   one certificate.
  </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SSL-CLIENT-CERTIFICATES"
>17.9.1. Using Client Certificates</A
></H2
><P
>   To require the client to supply a trusted certificate, place
   certificates of the certificate authorities (<ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
>s)
   you trust in the file <TT
CLASS="FILENAME"
>root.crt</TT
> in the data
   directory, and set the <TT
CLASS="LITERAL"
>clientcert</TT
> parameter
   to 1 on the appropriate <TT
CLASS="LITERAL"
>hostssl</TT
> line(s) in
   <TT
CLASS="FILENAME"
>pg_hba.conf</TT
>.
   A certificate will then be requested from the client during
   SSL connection startup.  (See <A
HREF="libpq-ssl.html"
>Section 31.17</A
> for a
   description of how to set up certificates on the client.)  The server will
   verify that the client's certificate is signed by one of the trusted
   certificate authorities.  Certificate Revocation List (CRL) entries
   are also checked if the file <TT
CLASS="FILENAME"
>root.crl</TT
> exists.
   
   (See <A
HREF="http://h71000.www7.hp.com/DOC/83final/BA554_90007/ch04s02.html"
TARGET="_top"
>http://h71000.www7.hp.com/DOC/83final/BA554_90007/ch04s02.html</A
>
   for diagrams showing SSL certificate usage.)
  </P
><P
>   The <TT
CLASS="LITERAL"
>clientcert</TT
> option in <TT
CLASS="FILENAME"
>pg_hba.conf</TT
> is
   available for all authentication methods, but only for rows specified as
   <TT
CLASS="LITERAL"
>hostssl</TT
>.  When <TT
CLASS="LITERAL"
>clientcert</TT
> is not specified
   or is set to 0, the server will still verify presented client
   certificates against <TT
CLASS="FILENAME"
>root.crt</TT
> if that file exists
   &mdash; but it will not insist that a client certificate be presented.
  </P
><P
>   Note that <TT
CLASS="FILENAME"
>root.crt</TT
> lists the top-level CAs that are
   considered trusted for signing client certificates.  In principle it need
   not list the CA that signed the server's certificate, though in most cases
   that CA would also be trusted for client certificates.
  </P
><P
>   If you are setting up client certificates, you may wish to use
   the <TT
CLASS="LITERAL"
>cert</TT
> authentication method, so that the certificates
   control user authentication as well as providing connection security.
   See <A
HREF="auth-methods.html#AUTH-CERT"
>Section 19.3.10</A
> for details.
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SSL-SERVER-FILES"
>17.9.2. SSL Server File Usage</A
></H2
><P
>    <A
HREF="ssl-tcp.html#SSL-FILE-USAGE"
>Table 17-3</A
> summarizes the files that are
    relevant to the SSL setup on the server.
   </P
><DIV
CLASS="TABLE"
><A
NAME="SSL-FILE-USAGE"
></A
><P
><B
>Table 17-3. SSL Server File Usage</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>File</TH
><TH
>Contents</TH
><TH
>Effect</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="FILENAME"
>$PGDATA/server.crt</TT
></TD
><TD
>server certificate</TD
><TD
>sent to client to indicate server's identity</TD
></TR
><TR
><TD
><TT
CLASS="FILENAME"
>$PGDATA/server.key</TT
></TD
><TD
>server private key</TD
><TD
>proves server certificate was sent by the owner; does not indicate
      certificate owner is trustworthy</TD
></TR
><TR
><TD
><TT
CLASS="FILENAME"
>$PGDATA/root.crt</TT
></TD
><TD
>trusted certificate authorities</TD
><TD
>checks that client certificate is
      signed by a trusted certificate authority</TD
></TR
><TR
><TD
><TT
CLASS="FILENAME"
>$PGDATA/root.crl</TT
></TD
><TD
>certificates revoked by certificate authorities</TD
><TD
>client certificate must not be on this list</TD
></TR
></TBODY
></TABLE
></DIV
><P
>    The files <TT
CLASS="FILENAME"
>server.key</TT
>, <TT
CLASS="FILENAME"
>server.crt</TT
>,
    <TT
CLASS="FILENAME"
>root.crt</TT
>, and <TT
CLASS="FILENAME"
>root.crl</TT
>
    are only examined during server start; so you must restart
    the server for changes in them to take effect.
   </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SSL-CERTIFICATE-CREATION"
>17.9.3. Creating a Self-signed Certificate</A
></H2
><P
>    To create a quick self-signed certificate for the server, use the
    following <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
> command:
</P><PRE
CLASS="PROGRAMLISTING"
>openssl req -new -text -out server.req</PRE
><P>
    Fill out the information that <SPAN
CLASS="APPLICATION"
>openssl</SPAN
> asks for. Make sure
    you enter the local host name as <SPAN
CLASS="QUOTE"
>"Common Name"</SPAN
>; the challenge
    password can be left blank. The program will generate a key that is
    passphrase protected; it will not accept a passphrase that is less
    than four characters long. To remove the passphrase (as you must if
    you want automatic start-up of the server), run the commands:
</P><PRE
CLASS="PROGRAMLISTING"
>openssl rsa -in privkey.pem -out server.key
rm privkey.pem</PRE
><P>
    Enter the old passphrase to unlock the existing key. Now do:
</P><PRE
CLASS="PROGRAMLISTING"
>openssl req -x509 -in server.req -text -key server.key -out server.crt</PRE
><P>
    to turn the certificate into a self-signed certificate and to copy
    the key and certificate to where the server will look for them.
    Finally do:
</P><PRE
CLASS="PROGRAMLISTING"
>chmod og-rwx server.key</PRE
><P>
    because the server will reject the file if its permissions are more
    liberal than this.
    For more details on how to create your server private key and
    certificate, refer to the <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
> documentation.
   </P
><P
>    A self-signed certificate can be used for testing, but a certificate
    signed by a certificate authority (<ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
>) (either one of the
    global <ACRONYM
CLASS="ACRONYM"
>CAs</ACRONYM
> or a local one) should be used in production
    so that clients can verify the server's identity. If all the clients
    are local to the organization, using a local <ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
> is
    recommended.
   </P
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